Check your shift cable wire, it could be snapped or stretched in that position. Also, the reverse gear in your transmission could be jammed or have a gear snapped off of its pivot. Taking it in to a shop might be your only option in this case, have good luck!

1997 silverado 5.7 will not shift in to reverse but will in to drive but sounde like it is not shifting in to higher gear when it speeds up , what could be the cause bands , linkige, computer? the fulid level is good not discolored or smell different